“Trig continues to light up our world,” the former DWTS contestant wrote on Instagram. “He IS the boss around here and continues to fill our days with so much laughter! He is stubborn and knows exactly what he wants - right this second.”

“Especially my dad who constantly stops by his school to make sure that he ate his lunch, and that his face is clean,” she wrote. “Trig is our definition of perfection and there isn’t one day that goes by without us feeling so thankful that God chose us to be his family.”

Courtesy of Bristol Meyer/Instagram

Former Republican vice presidential candidate Sarah Palin and her husband, Todd, welcomed Trig in April 2008, after finding out during her pregnancy that she was carrying a special-needs child.

The former Alaska governor shared a video of Trig hamming it up in their living room on Facebook on Tuesday. “Our family is blessed to celebrate Down Syndrome Day today and everyday!” she wrote. “Like Todd says, 'Had no idea he’d be king of this castle 24/7! Trig rules.’”

Earlier this month, Bristol, 26, shared the news that she and husband Meyer are expecting again. The pair are already parents of daughter Sailor, 15 months, and Bristol is also mom of son Tripp, 8, from her relationship with ex-fiance Levi Johnston.